In systems for editing and producing video and audio, it is often useful to carry various kinds of data that are adjunct to the audio and video signal data. Some of these data are associated with a video or audio sequence as a whole, or associated with a segment, and are not synchronous. Examples include descriptive metadata, such as information about the people involved in the production, date and location, as well as structural metadata, such as image format/type (e.g., HD, SD) and bit rate. However an increasing range of information in the form of data streams that are time-synchronized with the audio and video content is also being generated. This information is distinct from the audio and video portions of the signal, and represents additional information pertaining to the production and/or subject matter of the material.
In existing media editing and production systems, time-synchronous adjunct data are usually embedded within the audio or video signal. In digital video broadcasts, the data is often placed in the ancillary portion of the signal. In file-based media, such as those generated by cameras, disk recorders, video servers, and other video or audio acquisition and playback devices, the data is present in various forms within the media files, often as embedded portions of the video frames.
Such schemes for handling time-synchronous adjunct data streams limit the ability of editors to edit or otherwise manipulate the data streams independently of the picture and audio tracks.